It is well known that warm air forced into a room or derived from radiators tends to rise toward the ceiling of a room while cooler air tends to accumulate near the floor. This produces a temperature gradient that exposes individuals to colder room air and increases heat loss through ceilings and roofs. A corresponding problem arises during summer months. Individuals may experience a room as being hot because cool air discharged from air conditioning units tends to settle to the floor. Thermostat settings are often changed to obtain more heat or more cool air. In either case, the net result is increased energy consumption and higher cooling and heating costs.
It is also well known that ceiling fans can reduce room temperature gradients and consequently heating costs. The object is of course to mix hot air near a ceiling with cooler air near the floor to provide a comfortable temperature for individuals. Ceiling fans, however, are inefficient for such purposes. The air flow generated by a ceiling fan tends to spread horizontally far too quickly before reaching the floor. To reduce temperature gradients effectively, an air flow producer should ideally produce a vertical columnar air flow that actually reaches the floor. The air flow can then spread along the floor to entrain colder air along a floor, upward along walls, and then along a ceiling to the air flow producer for recirculation.